A conventional fuel injection nozzle for injecting and supplying fuel to an internal combustion engine has a body in which a nozzle hole is formed and a needle functioning as a valve element by opening and closing the nozzle hole. When an electromagnetic valve as an actuator operates a cylinder of the internal combustion engine is supplied with the fuel from the fuel injection nozzle.
Some of the conventional fuel injection nozzles have a nozzle hole group in which two or more solitary nozzle holes are located close to each other in order to improve diffusibility of the injected fuel, as described in JP-H9-88766 A and JP-S62-87665 A. In the nozzle hole group, solitary sprays from the solitary nozzle holes collide and interfere with each other. Thus, a group spray from the nozzle hole group is formed by the collision and the interference of the solitary sprays. The group spray improves penetration performance of the injected fuel toward the direction of the injection and the diffusibility of the injected fuel.
Recently, in order to increase an amount of the fluid injected per unit time, a fuel injection nozzle with more nozzle hole groups is under consideration. However, a negative effect caused by closeness between the neighboring nozzle hole groups becomes significant, as the number of the nozzle hole group increases too much.
Distances between the nozzle hole groups decrease as the number of the nozzle hole groups is increased so as to increase the amount of the injected fuel. A competition area from which the fuel is supplied to adjoining multiple nozzle hole groups enlarges as the distance between the nozzle hole groups becomes shorter.
As the competition area enlarges, pressures of the fuel entering the relevant adjoining nozzle hole groups decrease. This causes atomizing the fuel to become difficult and thereby black smoke to be increased. In addition, a distance between group sprays becomes shorter and therefore amounts of airs introduced to the group sprays become smaller. As a result, the black smoke further increases.